Nucleic acids (DNA & RNA)

1.

Nucleic acids (DNA & RNA)

2.

Watson and Crick discovered the double helix by building
models to conform to X-ray data
In April 1953, James Watson and Francis Crick shook the scientific world
with an elegant double-helical model or the structure of deoxyribonucleic
acid or DNA.
Watson and Crick began to work on a model of DNA with two strands, the
double helix.

3.

A gene is a small region in the DNA.
• Nucleic acids store and transmit hereditary information.
• There are two types of nucleic acids:
1)- ribonucleic acid (RNA);
2)- deoxyribonucleic acid (DNA).
• DNA also directs mRNA synthesis, thus, controls protein synthesis.
• Organisms inherit DNA from their parents.
– Each DNA molecule is very long and usually consists of hundreds to thousands of
genes.
– When a cell divides, its DNA is copied and passed to the next generation of cells.
• The mRNA interacts with ribosomes to direct the synthesis of amino acids in a
polypeptide (protein)

4. Structures of nucleic acids (DNA & RNA)

Structures of nucleic acids (DNA & RNA)
Bases
3 o 5
o P o
o
Phosphate
group
Base
o
5 CH2
4 H
H
3
H
2H
o
1
3
Purine
Deoxyribose
CH2
5
Adenine
(A)
Guanine
(G)
H
o P o
o
H
DNA
nucleotide
H
3
Base
o
Cytosine
(C)
Pyrimidine
H
H
H
Sugar-phosphate backbone
Thymine
(T)

5.

• The PO4 group of one
nucleotide is attached
to the sugar of the
next nucleotide in
line.
• The result is a
“backbone” of
alternating phopates
and sugars, from
which the bases
starts.
Fig. 16.3, Page 290

6. Nitrogenous bases

3
Nitrogenous bases
5
Nitrogenous bases
Hydrogen bonds
5
3
Sugar-phosphate
backbones
Cytosine
(C)
Guanine
(G)
Thymine
(T)
Adenine
(A)
Uracil (U)
Pyrimidines
Purine

7. The nucleic acid strand is a polymer of nucleotides

• Nucleic acids are polymers of monomers called nucleotides.
• Each nucleotide consists of three parts: a nitrogen base, a pentose sugar, and
a phosphate group.
• The nitrogen bases (rings of carbon and nitrogen) come in two types: Purines
and Pyrimidines.
• The pentose sugar joined to the nitrogen base is ribose in nucleotides of RNA
and deoxyribose in DNA.
• The only difference between the sugars is the lack of an oxygen atom on
carbon 2 in deoxyribose.

8.

• Polynucleotides are synthesized by connecting the sugars of
one nucleotide to the phosphate of the next with a
phosphodiester link.
• This creates a repeating backbone of sugar-phosphate units
with the nitrogen bases as appendages.
• The sequence of nitrogen bases along a DNA or mRNA polymer
is unique for each gene.
• Genes are normally hundreds to thousands of nucleotides
long.
• The linear order of bases in a gene specifies the order of amino
acids (the monomers of a protein).

9.

An RNA molecule is single polynucleotide chain (single strand).
DNA molecules have two polynucleotide strands (double strand) that spiral around to
form a double helix.

10.

• The sugar-phosphate
backbones of the two
polynucleotides are on the
outside of the helix.
• Pairs of nitrogenous
bases (one from each
strand) connect the
polynucleotide chains
with hydrogen bonds.
• Most DNA molecules
have thousands to
millions of base pairs (bP).

11. ribonucleic acid (RNA)

• a)- Messenger RNA (mRNA) is the blueprint for
construction of a protein.
• b)- Ribosomal RNA (rRNA) is the construction site where
the protein is made in the ribosome.
• c)- Transfer RNA (tRNA) is the truck delivering the proper
amino acid to the site at the right time.

12. DNA RNA

DNA
CH2
H
H
o
RNA
CH2
H
H
H
Deoxyribose sugar
(O on C2 is missed)
Deoxiribo-Nucleic-Acid
H
H
o
H
H
OH
Ribose sugar
(no missed O)
Ribo-Nucleic-Acid
Double stranded nucleic acid
Single stranded nucleic acid
Bases: A, G, C, T
Bases: A, G, C, U

13.

Repeated Sugar - Phosphate
DNA backbone
Sugar–Phosphate-Base
One nucleotide
Polynucleotide
DNA Molecule
DNA Double stranded
RNA single stranded
DNA
A
G
C
T
A
T
C
mRNA
T
U
C
G
A
T
U
A
G

14.

Comparison
Name
Function
DNA
DeoxyriboNucleic Acid
Long-term storage of
genetic information;
transmission of genetic
information to make other
cells and new organisms.
Structural
Features
B-form double helix. DNA
is a double-stranded
molecule consisting of a
long chain of nucleotides.
deoxyribose sugar
phosphate backbone
adenine, guanine, cytosine,
thymine bases
DNA is self-replicating.
Composition
of Bases and
Sugars
Propagation
Base Pairing
AT (adenine-thymine)
GC (guanine-cytosine)
RNA
RiboNucleic Acid
Used to transfer the genetic code
from the nucleus to the ribosomes
to make proteins. RNA is used to
transmit genetic information in
some organisms and may have
been the molecule used to store
genetic blueprints in primitive
organisms.
A-form helix. RNA usually is a
single-strand helix consisting of
shorter chains of nucleotides.
ribose sugar
phosphate backbone
adenine, guanine, cytosine, uracil
bases
RNA is synthesized from DNA on
an as-needed basis.
AU (adenine-uracil)
GC (guanine-cytosine)
14

15. Terminology

English
Russian
Kazakh
Nucleic acids
Нуклеиновая кислота
Нуклеин қышқылы
Deoxyribonucleic acid
Дезоксирибонуклеинов Дезоксирибонуклеин
ая кислота
қышқылы
Ribonucleic acid
Рибонуклениновая
кислота
Рибонуклеин қышқылы
Nucleotide
Нуклеотид
Нуклеотид
Nitrogenous bases
Азотистые основания
Азоттық негіздер
Phosphate group
Фосфатная группа
Фосфат тобы
Pentose sugar
Сахар пентоза
Қант пентоза
Purines
Пурины
Пуриндер
Pyrimidines
Пиримидины
Пиримидиндер
Amino acids
Аминокислоты
Аминқышқылы
Protein
Белок
Ақуыз